Rolls-Royce Electrical - A year on from acquiring Siemens eAircraft

Alongside the successful integration of engineers from Siemens into the global team, Rolls-Royce has refined the electrification focus and taken important strides forward in moving from technology demonstration to product certification.

Rolls-Royce has a bold ambition to play a crucial role in pioneering a resilient, net zero carbon future. We are aiming to become net zero carbon in our operations by 2030 and, more fundamentally, set an ambition to play a vital role in enabling the sectors in which we operate to reach net zero carbon by 2050 through the development of new products and technologies.

This includes an environmental strategy for aviation that has three strands: increasingly fuel-efficient products; supporting the development of environmentally friendly and sustainable aviation fuels; and pursuing novel and disruptive technologies, such as electrification.

Championing sustainable power and propulsion is a key part of this strategy and electrification has a considerable potential to transform mass transport through enablement of all-electric and hybrid-electric systems with lower CO2 footprints. For the first time, aviation is now exploring electrification for passenger-carrying aircraft to unlock environmental as well as many other socio-economic benefits. We believe that in a post-COVID world, people will still want to fly and will want to do so even more sustainably.

A global organization
It has now been a year, since we completed the acquisition of the electric and hybrid-electric propulsion activities of Siemens for aviation applications (formerly known as the eAircraft business).

The technology portfolio and skills were acquired to complement our existing technology and product developments in electrification aiming to bring a new class of quieter and cleaner air transport propulsion systems to the skiesRolls-Royce has a bold ambition to play a crucial role in pioneering a resilient, net zero carbon future.

The addition included 180 colleagues with vital skills and key know-how to augment our capability and technology portfolio. These skills and know-how can also be applied to support the development of products for adjacent markets such as micro-grids, hybrid-electric trains, marine and other industrial applications.

The Rolls-Royce Electrical team is now present in six countries: UK, USA, Singapore, Norway, Germany, and Hungary. At the start of the summer, global technology leads were assigned for the six main electrical technology streams with several countries represented. These employees are now pushing the development of the technology roadmaps, and the regional teams have started to support each other's product and technology development programs both through knowledge-exchange and manpower.

From rapid prototyping to product certification
With the acquisition, the former eAircraft teams' strength to rapidly bring electric propulsion systems from idea to prototype is now combined with Rolls-Royce existing electrical capabilities, expertise and years of experience in the development and certification of aerospace products.

This is all while the global aerospace propulsion electrification is transitioning from early technology demonstrator flights to the certification and commercial launch of first electric propulsion products. Now, a key and vitally important phase is beginning, which focuses on effectively combining our innovative technology with our long-standing and demonstrated pedigree in flight safety. This effort includes the development and qualification of a global and resilient supply chain that is certified to deliver airworthy components, as well as the development and implementation of a manufacturing base that is capable of producing our electrical products globally and at scale. Here, partnerships and collaboration with customers, strategic partners and regulators are critically important to our success.

A new focus
Both the former eAircraft and the formerly existing Rolls-Royce Electrical teams have been active across a broad spectrum of applications ranging from air taxis to regional aircraft. The focus has now been sharpened: target segments for the short-term will be the Small Propeller, Commuter and Urban Air Mobility markets.

For those, we are developing complete propulsion systems, i.e. not only the electrical machines but also the power electronics, cooling, cabling, power distribution and protection, power generation and control systems. We are further expanding our system solution offerings to include energy storage.

Addressing those new markets in the sub-megawatt propulsion class will enable us to grow value beyond today's core markets and scope of supply. In doing so, we are also enabling and ensuring that our existing businesses at the Rolls-Royce Group level have access to electrical systems technology, expertise and supply chain.

Rolls-Royce Electrical's ultimate objective is to launch the commercialisation of certified systems for all three market segments (Small Propeller, Commuter and Urban Air Mobility), within the next 3-5 years. Achieving this objective will draw from eAircraft legacy existing projects such as the support of the CityAirbus flight tests, the design, development, build, and test of two machine prototypes in the 1/2 MW range, the continued development of our M250H hybrid-electric system and the continuation of our activities on sub-100kW propulsion systems.

Towards a product for small propeller aircraft
Electric aircraft with two to four seats will bring a new experience to pilots and operators. They offer more sustainable and affordable flight training and environmentally friendly flight for sport aviators and enthusiasts; while thanks to their silent operation also respecting the needs of residential areas near small airports.

For this aircraft class, today's propulsion and battery technologies already allow for competitive aircraft performance and sufficient endurance for most missions. So far, only one small propeller aircraft type has been certified in the Light Sport Aircraft class (under 650 kg MTOW), but other companies are striving to certify their electric 2 or 4 seat aircraft also in the CS-23 / FAR-23 class, which allows for greater payload, within the next few years. This early market is especially competitive due to the comparatively low certification requirements. Rolls-Royce is running several research projects with small propeller aircraft.

The ACCEL project has set-out to excite and inspire the aviation world with the all-electric "Spirit of Innovation" aircraft by breaking the world record in speed for electric aircraft. In September we successfully conducted the Iron Bird tests and announced Bremont as the official timing partner.

At the end of June, we virtually "unveiled" the modified Tecnam P2010 aircraft with the H3PS propulsion system, the first parallel hybrid-electric propulsion system for General Aviation, together with Tecnam and Rotax. Here, the focus of this project is on developing the design of the hybrid-electric propulsion system and conducting extensive ground-testing to build our technological capabilities. This has already enabled our Hungarian colleagues to master the complex task of coupling an electric machine with a combustion engine in such a way that it participates in the propulsion system and can serve both as a motor or a generator. In this way, a significantly smaller combustion engine is enough for propulsion and fuel consumption is reduced.

Rolls-Royce is also gradually progressing from technology demonstration towards entry into market with competitive electrical products. Our first registration for certification is a 70kW Electric Propulsion Unit (EPU), which comprises an electric motor, the corresponding inverter and control system for certification with EASA and FAA.

The system, which is developed by the Rolls-Royce Electrical team based in Budapest, Hungary, has already had extensive flight testing in a demonstrator programme. We are aiming to certify this propulsion system for aircraft used in flight training and general aviation markets.

Electrifying regional air mobility and thin-haul cargo - a renewed commuter class
Electrifying commuter aircraft - aircraft with up to 19 seats covering regional distances and certifiable in the CS-23 class is a logical next step for us. Over the past several months, many companies have presented retrofit solutions as well as new aircraft designs for this aircraft class. They shall make regional air transport more sustainable and affordable, with the potential to reduce door-to-door travel time and help cater for the needs of logistics providers who experience continuously growing demand for just-in-time deliveries from e-commerce, while subjected to minimising their environmental footprint.

In this field, we are working on the ELICA project as part of a consortium that includes among others: the University of Naples, SmartUp Engineering, Siemens Industry Software NV and Air s.Pace GmbH,. The objective of this project is to develop a concept design for a 19 PAX commuter aircraft. While the University of Naples will carry out multidisciplinary optimisation and performance benefit analysis at the aircraft level, we will provide expertise in the area of the propulsion system architecture and electric machine design.

A typical twin engine 19-seater aircraft needs around 2x600 kW take-off power.

Based on a concept study for a hybrid-electric Dornier 228 Rolls-Royce Electrical have developed electric machine prototypes for this power-class and have obtained lab results from a 480kW electric motor and a 500kW generator.

Tecnam
We will work together with additional partners from the aerospace industry to derive the requirements for an electrical propulsion unit and energy storage system for this aircraft class, which we plan to launch as a product in the middle of this decade. One example is Tecnam, an Italian aircraft manufacturer, with whom we join forces in the development of the all-electric "P-Volt": an 11-seat aircraft for a variety of missions.

We are also working diligently on the propulsion system for the APUS i-5 with a full hybrid-electric-propulsion-system (M250H Hybrid) based on our M250 turbine engine as the prime mover. This turbine engine has been in operation for decades in the helicopter industry. The M250H integrates a 500kW electric generator and associated active rectifier power electronics, four distributed 150kW Electric Propulsion Units (EPUs) comprised each of an electric motor, the corresponding inverter and a gearbox that enables a quiet propeller operation.

The system further includes a modular Energy Storage System, a power distribution and protection, as well as an advanced power management controller and overall propulsion cooling system. Our goal is to bring the full M250H propulsion system to "flight-ready" status by mid-2022, with the aircraft being planned to fly in 2023. While the system is developed with the flexibility required to support multiple propulsion system architectures, for the purpose of the APUS i-5 flight, the M250H will be configured in a series topology. After that, it will transition to pre-commercial design and certification to expand our propulsion system offering for commuter aircraft, specifically catering for low propeller speeds.